# audio-timeline Spec Checklist

## Requirements

1. [ ] **Universal purity**
   - [ ] Scenario: Built dist references no platform globals
   - [ ] Scenario: Tests pass under both runtimes
2. [ ] **TimelineEngine construction and state snapshot**
   - [ ] Scenario: getState returns an immutable snapshot
   - [ ] Scenario: tracksVersion increments on track mutation
3. [ ] **Track model and CRUD operations**
   - [ ] Scenario: addTrack then removeTrack round-trips the track array
   - [ ] Scenario: Unknown track id throws AUDIO_TIMELINE_TRACK_NOT_FOUND
4. [ ] **Clip model and clip lifecycle**
   - [ ] Scenario: addClip places a clip on the named track
   - [ ] Scenario: Unknown clip id throws AUDIO_TIMELINE_CLIP_NOT_FOUND
5. [ ] **Clip drag with overlap constraint**
   - [ ] Scenario: Drag is clamped to avoid sibling overlap
   - [ ] Scenario: Zero constrained delta is a no-op
6. [ ] **Clip trim with minimum-duration guard**
   - [ ] Scenario: Right trim shortens duration within the floor
   - [ ] Scenario: Over-trim throws AUDIO_TIMELINE_INVALID_TRIM
7. [ ] **Clip split at a sample boundary**
   - [ ] Scenario: Split produces two contiguous clips
   - [ ] Scenario: Split outside the clip throws AUDIO_TIMELINE_INVALID_SPLIT
8. [ ] **Per-track mixer state**
   - [ ] Scenario: Volume is clamped and forwarded to the adapter
   - [ ] Scenario: Solo mutes non-soloed tracks
9. [ ] **Zoom levels and selection**
   - [ ] Scenario: zoomOut at the coarsest level is a no-op
   - [ ] Scenario: setSelection normalises a reversed range
10. [ ] **Loop region and transport playback**
    - [ ] Scenario: Playback follows the FSM transitions
    - [ ] Scenario: Invalid transport transition is rejected by the FSM
11. [ ] **Tempo and musical time**
    - [ ] Scenario: setTempo updates state and forwards to the adapter
12. [ ] **TimelineAdapter interface — plugin slot 5**
    - [ ] Scenario: NullTimelineAdapter satisfies the full interface
    - [ ] Scenario: Transport without an adapter throws AUDIO_TIMELINE_ADAPTER_NOT_SET
13. [ ] **Undo/redo via @suaveplan/undo**
    - [ ] Scenario: Mutation then undo restores prior state
    - [ ] Scenario: redo reapplies the undone command
14. [ ] **Transaction batching of undo commands**
    - [ ] Scenario: Committed transaction undoes as one step
    - [ ] Scenario: commitTransaction without an active transaction throws
15. [ ] **Incremental adapter updates on undo/redo**
    - [ ] Scenario: Same-count undo issues per-track updates
    - [ ] Scenario: Count-changing undo issues a full setTracks
16. [ ] **Typed timeline event surface**
    - [ ] Scenario: clipChange fires once per clip mutation
17. [ ] **Session save/load via @suaveplan/serialize**
    - [ ] Scenario: Session round-trips through serialize
18. [ ] **Zod boundary validation**
    - [ ] Scenario: Invalid clip is rejected at the boundary
19. [ ] **Structured error codes**
    - [ ] Scenario: Every registered code is thrown by a call site
20. [ ] **OpenTelemetry instrumentation**
    - [ ] Scenario: Instrumentation is inert without an exporter
21. [ ] **AbortSignal propagation**
    - [ ] Scenario: Pre-aborted signal short-circuits init
22. [ ] **Subpath exports per feature module**
    - [ ] Scenario: Each feature module is independently importable